CELLS. 
25 
assumes more and more the appearance of a star, as 
shown in Fig. 15. In the Rush we have a very beau- 
tiful example of this form of tissue, the cell being 
FIG. 15 . 
FIG. 16 . 
Stellate cells from fully developed 
petiole of Sparganium ramosum ; a a a, 
lacunae. 
Stellate cells from the stem of a 
Rush; a a a, black lines indicating 
the cell -walls. 
reduced to a six-rayed star, as shown in Fig. 16, but 
the remains of the cell-wall, indicated by the black 
lines, aa , are always present. By this alteration in 
the shape of the cells, the stem becomes lighter, and in 
this way the large receptacles for air, common in most 
water plants, are formed. 
Very striking specimens of 
the filamentous form of tis- 
sue are obtained from many 
of the fungi, as the com- 
mon edible Mushroom , in 
which the cells are of a long 
oval figure, and joined end 
to end, as shown in Fig. 1 7 ; 
Elongated cells of the Mushroom, but in the Boletus ignidrius 
